1. Field of Invention
The present invention relates to TAB (Tape Automated Bonding) technology in which integrated circuit element, such as, for example, ICs, LSIs and other electronic parts, are mounted on a film carrier.
2. Description of Related Art
Recent liquid crystal display apparatus typically use TAB for connecting their driver circuits to LCD cells, in which driver ICs are mounted on what is generally called a tape carrier package, or a COG (Chip On Glass) technology in which driver ICs are directly connected to the substrate. Tape carrier packages are small and thin compared with other types of packages and suitable for high-density mounting. There are also other advantages. For example, electrical examinations can be performed on the film carrier tapes, and the tape carrier packages can be bent for mounting. Accordingly, they are used not only for liquid crystal display apparatus, but also for a variety of other electronic apparatus.
Conventional tape carrier packages include, as shown in FIG. 11, a film carrier 1 formed from polyimide or the like defining a device hole 3 that is larger than the size of an integrated circuit element 2 to be mounted on the film carrier 1. Inner leads 4 protruding into the interior of the device hole are connected to electrodes of the integrated circuit element 2 through bumps 5.
Furthermore, to prevent cross-talk between the inner leads 4 and contact between the inner leads 4 and the integrated circuit element 2, thereby improving reliability, a protection resin 6 is used to cover the inner leads 4 and the surface of the integrated circuit element 2. This is shown in FIG. 12, which is a cross-sectional view taken along lines 12--12 of FIG. 11. The electrodes or the bumps 5 are typically disposed along peripheral edges of the integrated circuit element 2 to shorten as much as possible the length of the inner leads 4 that are in the form of cantilevers.
Also, as described, for example, in Japanese Laid-Open Patent Application No. SHO 63-95639, when an integrated circuit element 2 having many large electrodes is mounted, a known structure is used. In the structure, a lead support section that extends into a device hole is provided on a film carrier, and inner leads are in part extended over the lead support section.
In recent years, to further reduce the size of the above-described tape carrier packages, a film carrier 1 is provided with a device hole 3 that is smaller than the size of an integrated circuit element 2 to be mounted, and inner leads 4 protruding in the device hole are connected to electrodes that are provided adjacent the central area of the integrated circuit element 2 through bumps 5. See FIG. 13.
However, in the above-described tape carrier package, the device hole is rectangular in its plan view. In particular, when the inner leads 4 are provided along only two opposing edges of the device hole 3, and the inner leads 4 are connected to the integrated circuit element 2, no inner leads to be connected to the integrated circuit element 2 are present along edges located at the ends of these opposing edges. When protection resin is coated on the inner leads 4 and the surface of the integrated circuit element 2 where the inner leads 4 are connected to the bumps 5, the inner leads 4 act as resistance and prevent the flow of the protection resin 6. Where there are no inner leads 4 connected to the bumps 5, only a separation between the film carrier 1 and the integrated circuit element 2 provides a resistance factor that influences the fluidity of the protection resin 6.
Therefore, the condition of areas coated with the protection resin 6 varies depending on the presence or absence of the inner leads 4 that are connected to the bumps 5. As a result, when the protection resin 6 is coated on the surfaces of the integrated circuit element 2 and the inner leads 4, the protection resin 6 flows through a gap 9 toward the peripheral edges of the integrated circuit element 2, and the flow width 8 of the protection resin 6 becomes greater. As a consequence, a recess portion 7 is generated in the protection resin, as shown in FIG. 14, and the required thickness of the protection resin 6 may not be provided on the entire surface.